Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-06-06 Thread H. Peter Anvin
The USB debug port is nice once you get it to work. Assumes they haven't done anything clever like hide the special port behind a hub... Sent from my tablet, pardon any formatting problems. > On Jun 6, 2014, at 1:24, Borislav Petkov wrote: > >> On Fri, Jun 06, 2014 at 10:17:26AM +0200, Peter

Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-06-06 Thread H. Peter Anvin
Yes, but now you need a custom adapter. Some have used a phono plug for the absolute minimum 3 wires. However, no standards... Sent from my tablet, pardon any formatting problems. > On Jun 6, 2014, at 2:35, Peter Zijlstra wrote: > >> On Fri, Jun 06, 2014 at 10:24:20AM +0200, Borislav Petkov

Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-06-06 Thread Peter Zijlstra
On Fri, Jun 06, 2014 at 10:24:20AM +0200, Borislav Petkov wrote: > Well, with all the other crap they put in modern machines, how hard it > is to put a goddam stupid serial line out everywhere...? WTF do I need a > goddam adaptive keyboard and other idiotic bling-bling if I can't have a > simple se

Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-06-06 Thread Borislav Petkov
On Fri, Jun 06, 2014 at 10:17:26AM +0200, Peter Zijlstra wrote: > Hopefully the EFI pstore thing will work out, but I've already heard > that can wear out very quickly and render your machine a brick :-( And not only that - write speed is awfully low. I hear you might be ok to record an oops or so

Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-06-06 Thread Peter Zijlstra
On Wed, May 07, 2014 at 06:40:14PM +0200, Ingo Molnar wrote: > Agreed, that's a very good point. > > Also, consider the following holistic argument, what is easier to > achieve, when looking at an oops and not seeing the bug: > > - if only I had more information > - if only I had less inform

Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-05-07 Thread Peter Zijlstra
On Wed, May 07, 2014 at 07:18:22PM +0200, Ingo Molnar wrote: > > Conclusion: > > So to me #4 looks best, and it's 16 lines instead of 31. Not as > compact as your mockup that has 13 lines, but pretty close. > > (I'd also do the color tricks on #6, but that's more technically > challenging and

Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-05-07 Thread Ingo Molnar
* Linus Torvalds wrote: > So to take your example, it might be something like this > > arch_trigger_all_cpu_backtrace+0x3c -> do_raw_spin_lock+0xb7 > -> _raw_spin_lock_irqsave+0x35 -> ? prepare_to_wait+0x18 > -> prepare_to_wait+0x18 -> ? generic_make_request+0x80 > -> ? unmap_underlying_meta

Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-05-07 Thread Ingo Molnar
* Frederic Weisbecker wrote: > On Sun, Apr 27, 2014 at 02:08:20PM +0200, Ingo Molnar wrote: > > > > * Richard Yao wrote: > > > > > Stack traces are generated by scanning the stack and interpeting > > > anything that looks like it could be a pointer to something. We do > > > not need to do t

Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-04-30 Thread Frederic Weisbecker
On Sun, Apr 27, 2014 at 02:08:20PM +0200, Ingo Molnar wrote: > > * Richard Yao wrote: > > > Stack traces are generated by scanning the stack and interpeting > > anything that looks like it could be a pointer to something. We do > > not need to do this when we have frame pointers, but we do it

Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-04-27 Thread Richard Yao
On Apr 27, 2014, at 4:08 PM, Linus Torvalds wrote: > On Sun, Apr 27, 2014 at 5:08 AM, Ingo Molnar wrote: >> >> So it's useful information for hairy bugs and it would be sad to >> remove them. > > I tend to agree. I've often found the left-overs to be good clues > about what just got called. A

Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-04-27 Thread Linus Torvalds
On Sun, Apr 27, 2014 at 5:08 AM, Ingo Molnar wrote: > > So it's useful information for hairy bugs and it would be sad to > remove them. I tend to agree. I've often found the left-overs to be good clues about what just got called. Although equally often it's another kind of clue entirely: that the

Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-04-27 Thread Richard Yao
I happened to write this with an email client that used Rich Text, which the LKML rejected, so I am resending it in plaintext format. My future replies will be made in plaintext, which is what my normal development system’s email client does. On Apr 27, 2014, at 8:08 AM, Ingo Molnar wrote: >

Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-04-27 Thread Peter Zijlstra
On Sun, Apr 27, 2014 at 02:08:20PM +0200, Ingo Molnar wrote: > For example if we used more horizontal separation in the output > format: > > Call Trace: > [<79018d24>] arch_trigger_all_cpu_backtrace+0x3c/0x64 > [<7916a34c>] do_raw_spin_lock+0xb7/0xe8 > [<792b9412>] _raw_spin_lock_irqsave+0

Re: [PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-04-27 Thread Ingo Molnar
* Richard Yao wrote: > Stack traces are generated by scanning the stack and interpeting > anything that looks like it could be a pointer to something. We do > not need to do this when we have frame pointers, but we do it > anyway, with the distinction that we use the return pointers to mark

[PATCH] x86/dumpstack: Walk frames when built with frame pointers

2014-04-26 Thread Richard Yao
Stack traces are generated by scanning the stack and interpeting anything that looks like it could be a pointer to something. We do not need to do this when we have frame pointers, but we do it anyway, with the distinction that we use the return pointers to mark actual frames by the absence of a qu